Found my cooling issue

Heating, Cooling & AC

  1. Jeff Erwin

    Jeff Erwin FBBO Gold Member FBBO Gold Member

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    OK, I've read all the articles about how thermostats work and I believe I understand it. So my 440x6 would not move the temp gauge. I did all the required testing, grounding the sensor made the gauge move so the wiring and gauge worked. I replaced the sensor because they're cheap and easy to replace. Still no movement until I stopped the engine and waited 60 seconds. Turning the car back on had the temp gauge at about the 1/3 mark. It quickly scooted back to 0 when I started the engine.

    So I decided to replace the 180 thermostat with the 195 as Dodge specified for this engine.

    The existing thermostat was stuck open. It was one of those 'fail open' types and had been in the engine for a whopping 3 months. Stuck open meant there was no regulation on the cooling and the engine was unable to reach operating temp.

    New thermostat and the gauge works. With a 195 it runs up to the 90% mark before backing back down to about the 60% range.

    Now I really understand.
     
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    • Don Frelier

      Don Frelier FBBO Gold Member FBBO Gold Member

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      :thumbsup:

      In the future a quick check on the thermostat is the upper hose should remain cold for maybe 5 minutes or so then it will get hot when the thermostat opens.
      Similarly if you start it cold with the cap off the radiator you shouldn't see any water movement until the thermostat opens.
      I've found the gauges in my Chrysler cars to be very reliable.
       
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      • goodolboydws

        goodolboydws New Member

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        Don't feel too badly, a lot of people take thermostats for granted as they are so simple a mechanism. But, do you know for certain if yours HAD EVER been working properly?

        I had a bum one right out of the box on my very first car, (one that had multuiple manifold/carb/cam configurations over time) and have water-bath tested EVERY one on a keeper since then-before installing them.

        Out of under 50 NEW ones I've installed in our family's personal cars over the years, (both foreign and domestic) a sizeable percentage of those new ones that were WORKING were significantly out of spec. As in more than 10 degrees off.

        Some OPENED FULLY at too low of a temp, others NEVER opened fully, some (once open) stayed either fully or partially open when, (according to their specs) should have been tightly closed back down and yet others didn't BEGIN to crack open until well above spec'd temp.
         
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        • Jeff Erwin

          Jeff Erwin FBBO Gold Member FBBO Gold Member

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          In retrospect I don't think it was ever working, probably stuck open the first time it opened. It was one of these 'safety' thermostats that fails open. Didn't realize it failed immediately.

          My 195 seems to be working perfectly. The temp gauge runs up to about the 90% point, then the thermostat opens and it settles at about the 50% point.
           
        • bm02tj

          bm02tj Well-Known Member

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          I test them in a pot of water on the stove with a thermometer to check opening temps and full open temp
           
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          • Cranky

            Cranky Henchman #27 Staff Member FBBO Gold Member

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            Used to run a 180 in my 71 340 Cuda in the summer and a 195 in the winter. Winters here ain't bad usually but still nice to have heat when it's around 50 outside. Anyways, never got a bad once but gave up on my diesel. It's the same way....won't heat up so I just block the radiator. Down side to that is if it's sunny out or need to run the AC or defroster, the AC system doesn't do well when stopped at a light since the fan can't pull air through. I can block that thing 90% on a 70 degree day and the engine runs right where it should as long as it's moving but in stop and go traffic it never goes higher than 195 unless I'm stopped for several minutes.
             
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